1,5-diethenylnaphthalene compounds and bifunctional primers for anionic polymerization prepared therefrom

ABSTRACT

Bifunctional primer naphthalene compounds having the formula: ##STR1## wherein M&#34; is an alkali metal, preferably sodium or lithium, and R 1  and R 2  are, e.g., alkyl radicals, are prepared from corresponding 1,5-diethenylnaphthalene derivatives, and are well suited for the improved anionic polymerization of diene, vinylaromatic and/or (meth)acrylic monomers.

This application is a divisional of application Ser. No. 08/409,989,filed Mar. 24, 1995, now U.S. Pat. No. 5,674,799.

BACKGROUND OF THE INVENTION

1. Field of the Invention:

The present invention relates to novel 1,5-diethenylnaphthalenecompounds, to a process for the preparation thereof, and to theconversion of same via reaction with an organic alkali metal compoundinto bifunctional primers for anionic polymerization mechanisms.

2. Description of the Prior Art:

Organic alkali metal compounds, such as organodilithium compounds, areknown to this art as especially advantageous bifunctional primers foranionic polymerization reactions, since the three-step procedurerequired to prepare ABA sequenced copolymers by monofunctional primingis reduced by one step through the use of bifunctional primers. Theselatter are also important in copolymerization reactions, when the secondmonomer cannot re-initiate polymerization of the first.

Numerous sequenced copolymers have been prepared using alkali metalnaphthalides as bifunctional primers. These bifunctional primers areefficacious only in polar reaction media, such a tetrahydrofuran, inparticular for the polymerization of diene monomers. However, theycannot provide a polydiene microstructure having a high degree of1,4-configuration (Cis- or trans-).

In the event that a special microstructure, in general a 1,4-cisaddition for polydienes, is desired, the anionic polymerization must becarried out in a nonpolar solvent utilizing the alkali metal, e.g.,lithium, as the counter-ion. Unfortunately, and probably because ofassociated reagents, organic alkali metal compounds, such asorganodilithium compounds, exhibit a low level of solubility inhydrocarbonaceous solvents. Tests for increased solubility using verysmall amounts of ether or amines indicated that these additives affectthe microstructure of the diene block. The disadvantage presented by theseeding technique is a high dispersion index for the central sequence.

To date, many compounds have been described for their possible use asbifunctional lithium-containing primers which are soluble in nonpolarsolvents.

For example, U.S. Pat. No. 4,200,718, at column 14, describes thecompound corresponding to the formula: ##STR2## which is reacted withsecondary butyllithium to prepare2,7-naphthalenediylbis(3-methyl-1-phenylpentylidene!bis(lithium), aprimer used for the anionic polymerization of butadiene.

Turgut Nugay and Savas Kucukyavuz, in Polym. International, 29, 195(1992), describe the preparation of 1,5-diethenylnaphthalene andreaction thereof with secondary butyllithium in n-heptane, in theabsence of any polar additive, thereby producing1,5-bis(1-lithio-3-methylpentyl)naphthalene. This compound was easilyisolated and the soluble monofunctional compounds removed. Whendissolved in benzene (solubility: 3.2×10⁻² mole/liter), it was used aprimer for the sequenced copolymeriztion of isoprene and styrene.

Nonetheless, need continues to exist to provide even better solubilityin nonpolar solvents and enhanced control over the bifunctionality ofsuch 1,5-bisubstituted naphthalene-containing primers.

SUMMARY OF THE INVENTION

Accordingly, a major object of the present invention is the provision ofnovel 1,5-diethenylnaphthalene compounds that avoid or conspicuouslyameliorate the above disadvantages and drawbacks to date characterizingthe state of this art.

Briefly, the present invention features compounds having the formula(I): ##STR3## in which R¹ is a linear, branched, or cyclic alkyl radicalhaving from 1 to 12 carbon atoms, or a substituted or unsubstituted arylradical.

The alkyl radicals R¹ are preferably methyl radicals; the aryl radicalsR¹ are preferably phenyl radicals.

The present invention also features a process for preparing thecompounds (1), comprising, in a first step, reacting a compound havingthe formula (II): ##STR4## with a compound having the formula (III):

    R.sup.1 --M                                                (III)

in which R¹ is as defined above; and M is an alkali metal or M'Hal (M'representing an alkaline earth metal, and Hal, a halogen), thereafterhydrolyzing the derivative thus formed to provide a compound having theformula (IV): ##STR5## and, in a second step, dehydrating the compoundhaving formula (IV), thereby providing the desired final product.

DETAILED DESCRIPTION OF BEST MODE AND PREFERRED EMBODIMENTS OF THEINVENTION

More particularly according to the present invention, in the first stepof the process aspect thereof, to add the organometallic compound (III)to the compound (II), the respective reagents are employed in amounts ofat least two moles of compound (III) per 1 mole of compound (II),preferably using an amount of compound (III) slightly in excess of thestoichiometric amount, such addition being carried out in an aproticsolvent medium (e.g., tetrahydrofuran, toluene, ethyl ether, benzene,ethylbenzene, cyclohexane, and mixtures thereof), the temperature beingregulated depending on the reagents used, and the reaction time beingapproximately 6 to 24 hours. This reaction is followed by hydrolysiscarried out under conditions resulting in the deactivation of thereaction product, whether by means of methanol acidified with aceticacid or via the use of a water/ice/hydrochloric acid mixture.

The second step entailing dehydration can be carried out, for example,in an acetic acid/sulfuric acid medium concentrated under reflux, theproportion of sulfuric acid in comparison with the acetic acid being0.1% to 5% by weight; or in a toluene/paratoluene sulfonic acid medium.

The present invention also features a bifunctional primer, namely, ofthe product of the reaction of the compound of formula (I), as indicatedabove, with a compound having the formula (V):

    R.sup.2 --M"                                               (V)

in which M" is an alkali metal, notably lithium or sodium; and R² is aC₁ -C₆ alkyl radical, a C₅ -C₁₂ cycloalkyl radical or an aromaticradical, with the proviso that the compound (V) can be an anionicpolymer comprising a terminal carbanion R² and the counter-ion M", saidbifunctional primer being represented by the following formula (IV):##STR6## in which R² preferably is a secondary butyl group.

When M" represents Li and when the organolithium compound (V) is anartionic polymer, thus affording a bifunctional primer providingstar-shaped polymers, the polymeric carbanion R² may be a vinylaromaticpolymer carbanion, such as polystyrene and poly(alpha-methylstyrene), ora diene-containing polymer carbanion such as polybutadiene andpolyisoprene.

The bifunctional primer is synthesized by reacting compounds (I) and (V)in amounts of at least 2 moles of compound (V) per 1 mole of compound(I), in particular utilizing a slight excess of compound (V) as comparedwith the stoichiometric amount in a purified aprotic solvent medium(examples of solvents are provided above with reference to the additionof the organometallic compound (III) to compound (II)), with thesubsequent polymerization being carried out by the direct addition ofmonomers to the reaction medium. A slight excess of compound (V) givesrise to deactivation of the residual protic impurities in the reactionmedium.

Too, the present invention features a process for anionic polymerizationof at least one polymerizable monomer with an alkali metal compoundemployed as the primer, this process being characterized in that theprimer used is a bifunctional primer, as indicated above.

By "polymerizable monomers" are intended diene-containing,vinylaromatic, and (meth)acrylic monomers.

By the expression "diene-containing monomer" is intended a dieneselected from among conjugated linear or cyclic dienes having from 1 to20 atoms of carbon. Exemplary thereof are butadiene, isoprene,1,3-pentadiene, cyclopentadiene, and 6,7,8,9-tetrahydroindene. Thepreferred monomers are butadiene and isoprene.

By the term "vinylaromatic" monomers are intendedethylenically-unsaturated aromatic monomers. Exemplary thereof arestyrene, vinyltoluene, alphamethylstyrene, 4-methylstyrene,3-methylstyrene, 4-ethylstyrene, 3,4-dimethylstyrene,3-tertbutylstyrene, and 2-vinylnaphthalene. Hydroxylated styrenederivatives can also be employed, such as 4-methoxystyrene,2-hydroxymethylstyrene, and 4-ethoxystyrene, provided that the OHfunction is protected. The preferred monomer is styrene.

By the term "(meth)acrylic monomer" is intended a monomer selected fromamong the (meth)acrylates having the following respective formulae:##STR7## in which R_(e) is a linear or branched, primary, secondary, ortertiary C₁ -C₁₈ alkyl radical, a C₅ -C₁₈ cycloalkyl radical, a (C₁ -C₁₈alkoxy) C₁ -C₁₈ alkyl radical, a (C₁ -C₁₈ alkylthium) C₁ -C₁₈ alkylradical, and aryl and aralkyl radicals, these radicals optionally beingsubstituted by at least one atom of halogen and/or at least one hydroxylgroup after protecting this hydroxyl group, said alkyl groups beinglinear or branched, glycidyl, norbornyl, isonorbornyl (meth)acrylates,and di-(C₁ -C₁₈ alkyl)-(meth)acrylamides.

Exemplary methacrylates having the above formula include methyl, ethyl,2,2,2-trifluoroethyl, n-propyl, isopropyl, n-butyl, secondary butyl,tertiary butyl, n-amyl, 1-amyl, n-hexyl, 2-ethylhexyl, cyclohexyl,octyl, 1-octyl, nonyl, decyl, lauryl, stearyl, phenyl, and benzylmethacrylates. The preferred methacrylic monomer is methyl methacrylate.

Exemplary acrylates having the above formula include methyl, ethyl,n-propyl, isopropyl, n-butyl, secondary butyl, tertiary butyl, hexyl,2-ethylhexyl, isooctyl, 3,3,5-trimethyhexyl, nonyl, isodecyl, lauryl,octadecyl, cyclohexyl, phenyl, methoxymethyl, methoxyethyl,ethoxymethyl, and ethoxyethyl acrylates.

In general, in a step carried out following preparation of an activepolymer sequence, when such sequence is formed from at least onevinylaromatic and/or diene-containing monomer, the latter may be reactedwith at least one vinylaromatic, (meth)acrylic, or diene-containingmonomer, if required in the presence of a ligand, in order to obtain atrisequenced copolymer. This ligand may be selected, on the one hand,from among the alkali metal or alkaline earth metal salts, e.g.,chlorides, fluorides, bromides, iodides, borides, and, on the other,among the alkali metal organic salts, e.g., alcoholates.

Illustrative thereof is, in particular, the anionic polymerization of atleast one diene monomer in the presence of a nonpolar solvent, e.g.,toluene, benzene, ethylbenzene, and mixtures thereof, as required with asmall amount of cyclohexane. After preparing the activepolydiene-containing sequence, this sequence may be reacted with atleast one vinylaromatic or (meth)acrylate monomer, if necessary in thepresence of a ligand such as described in published French PatentApplication No. 92/14,318, to produce a trisequenced copolymer.

Also illustrative is the production of trisequenced poly(methylmethacrylate)/vinylaromatic or diene-containing polymer/poly(methylmethacrylate) polymers.

Typically, polymerization of a diene-containing monomer is carried outat a temperature ranging from -80° C. to +100° C., and, preferably, at atemperature ranging from -70° C. to +70° C., and polymerization of a(meth)acrylate monomer is carried out at a temperature ranging from -80°C. to +60° C. and, preferably, at a temperature ranging from -70° C. to20° C. The polymerization of a vinylaromatic monomer is typicallycarried out at a temperature ranging from -80° C. to +100° C., and,preferably, at a temperature ranging from -70° C. to +70° C.

The polymerization of a diene-containing monomer is normally carried outover a time period of 1/2 hour to 24 hours; polymerization of a(meth)acrylate monomer is carried out over a period of time of less than1 hour, and that of a vinylaromatic monomer, between 1/2 hour and 24hours.

The protonic compounds introduced at the end of polymerization todeactivate the active polymer sites may be selected from among water,alcohols, and acids. A preferred such material is acidified methanol.

Subsequently, it is possible to at least partially reduce the residualunsaturation of the polydiene sequences via conventional hydrogenationtechniques, to improve various of the properties thereof, in particularstability vis-a-vis ultraviolet light.

The trisequenced (co)polymers and copolymers, such as those preparedusing the bifunctional primer according to the invention, are useful forsuch well known applications as elastomers, thermoplastic elastomers,compatibility-enhancing agents, etc. As thermoformable materials, theymay be converted by techniques such as extrusion and injection molding,to provide shaped articles such as fibers, coatings and coverings,shoes, etc. The aforesaid sequenced copolymers, in which the methacrylicmonomer is methyl methyacrylate having a high degree of heat-resistance,can be used as pressure-sensitive adhesives and as agents for enhancingthe shock- and heat-resistance of polymers, as described in publishedFrench Patent Application No. 92/14,318.

In order to further illustrate the present invention and the advantagesthereof, the following specific examples are given, it being understoodthat same are intended only as illustrative and in nowise limitative.

In said examples to follow, all parts and percentages are given byweight, unless otherwise indicated, and the following abbreviations havebeen employed:

DAN=1,5-diacetylnaphthalene

PhLi=phenyllithium

BPEN=1,5-bis(phenylethenyl)naphthalene,

BPHEN=1,5-bis(1-phenyl-1-hydroxyethyl)naphthalene,

BMEN=1,5-bis(-methylethenyl)naphthalene,

BMHEN=1,5-bis(1-methyl-1-hydroxyethyl)naphthalene,

St=styrene,

BD=butadiene,

sec. BuLi=secondary butyllithium,

THF=tetrahydrofuran,

SBS=trisequenced styrene-butadiene-styrene copolymer

EXAMPLE 1

Preparation of BPEN: ##STR8##

DAN was prepared via the method described by R. Stephen in Chem. Ber.,909 (1957) 296, by reacting acetyl chloride with naphthalene in thepresence of aluminum trichloride. The product was crystallized in ethylalcohol (yield: 35%), and had a melting point of 131.9° C.

In the next step, 5 grams (24 mmoles) DAN were dissolved in 50 ml driedTHFand stored in a flask under a nitrogen atmosphere. At the same time,200 mlTHF were cryodistilled in a 500-ml reaction vessel, then 50 mmolesPhLi (2Msolution in a benzene/ether mixture) were transferred to thevessel using asyringe. The DAN in solution in the THF was then added tothe reaction medium at 5° C. The solution first turned a deep green,then a brick color (heterogeneous reaction). The reaction was carriedout for 24 hours, then stopped by adding methanol containing 2.8 mlacetic acid.

The white acetic acid Li salt precipitate was filtered. A clear yellowsolution was then separated out, and the solvent evaporated using arotaryevaporator. The remaining product was a mixture of crystalline andoily compounds, which were identified by means of NMR ¹ H and FTIR asbeing BPHEN, a naphthalene compound containing 1-hydroxyethyl andethenyl groups, and a small amount of DPEN. The mixture was thendissolved in 70 ml acetic acid heated to reflux temperature. 0.1 mlconcentrated H₂ SO₄ was added using a pipette. The solution was cooled,and then a very pale yellow crystalline product was separated out,washed with cold acetic acid, and dried. The remaining fraction of theproduct was obtainedafter evaporating 1/3 of the solvent. A total of 3.1grams BPEN (39% compared with the DAN) were obtained (melting point:184° C.).

NMR ¹ H 200 MHz (CDCl₃) δ 7.80-7.27 (16H, aromatic) 5.99 (double, 1H,═CH₂) 5.40 (double, 1H, ═CH₂).

EXAMPLE 2

Synthesis of BMEN: ##STR9##

3 grams DAN (14.2 mmoles) were dissolved in 200 ml of a toluene/diethylether mixture (1:1, v/v). The reaction vessel was washed with drynitrogen, and 12 ml methyl magnesium bromide (excess amount, 3M solutionin diethyl ether) were dripped in using a syringe. A yellow precipitateformed immediately. The reaction medium was heated to refluxtemperature, and the reaction continued for 24 hours.

The product was then poured over 200 grams of a water/ice mixturecontaining 20 ml HCl; a white precipitate formed. The solids werefiltered(conversion rate exceeding 90%) and characterized using NMR ¹ Hand FTIR, which indicated BMHEN formation.

6.4 grams BMHEN were dissolved in acetic acid and heated to refluxtemperature. 0.1 ml concentrated H₂ SO₄ was added. The solution wascooled and filtered. A red solid was washed using cold acetic acid.BMHEN yield was 8%.

NMR ¹ H 200 MHz (CDCl₃) 7.81-7.26 (6H, aromatic) 5.99 (double, 1H, ═CH₂)5.40 (double, 1H, ═CH₂).

EXAMPLE 3 ##STR10##

0.1 gram (3×10⁻⁴ mole) BPEN was placed in a polymerization reactionvessel, preliminarily vacuum-dried for 5 hours. 500 ml purified, driedtoluene were added by cryodistillation.

To solubilize the BPEN in toluene, the temperature was increased from-70° C. to 0° C. While conducting the operation in an inert nitrogen andargon atmosphere, several drops of a secondary BuLi solution were addedto the reactive mixture until a light green color was maintained. Thisstep was intended to remove residual impurities.

At this temperature of 0° C., 0.45 ml of a 1.4 molar solution ofsecondary BuLi (i.e., 6.3×10⁻⁴) was then added to the reaction mixture,which immediately acquired a dark green color. At this stage, neither aprecipitate nor a colloidal dispersion was seen to form during astorageperiod of several hours. This observation evidenced that the primerwassoluble in toluene at 0° C.

Next, 28.5 grams (0.53 mole) butadiene were cryodistilled in thereaction vessel at -40° C. After adding the butadiene, the temperaturewas first increased to 0° C., at which level the appearance of aprecipitate was observed, then to +30° C., at which temperature thisprecipitate solubilized. The reaction then continued for 24 hours at+30° C.

A sample of the polybutadiene formed at this stage was collected andanalyzed using NMR and GPC. It had the following properties:

(a) Mn=99,000;

(b) 1,4-structure=91.5%.

The molar mass, which, as calculated, approximated the theoreticalmolecular weight (theoretical Mn=95,000) confirmed the enhancedsolubilityand improved regulation of the bifunctional nature of theprimer.

10 grams (0.096 mole) preliminarily-purified styrene were added to thereaction medium, which became viscous. The appearance of an orangecolor, characteristic of polystyryl anions, was observed. The reactioncontinued for 24 hours at ambient temperature before being stopped usingmethanol. The SBS copolymer which was recovered by precipitation inmethanol, filtration, and drying, was then analyzed by NMR and GPC.

The SBS copolymer had the following properties:

(a) PBD content: 69% by mass,

(b) PSt content: 31% by mass,

(c) Mn=143,000 (value calculated based on Mn in the PBD sequence and thecomposition obtained by NMR),

(d) Polydispersity index: 1.50.

EXAMPLE 4 ##STR11##

The procedure of Example 3 was repeated, using 0.2 gram BPEN (6×10⁻⁴mole) and 0.90 ml (12.6×10⁻⁴ mole) of secondary BuLi. The proportions ofbutadiene and styrene were identical tothose reported in Example 3.

The polybutadiene PBD sequence obtained under these conditions had an Mnvalue of 47,600 and a 1,4-structural content of 92.9%. The very highcorrespondence between the calculated and theoretical molecular weight(theoretical Mn=47,500) confirmed the improved solubility andbifunctionalnature of the primer.

The SBS copolymer had the following properties:

(a) Polybutadiene content: 71% by mass,

(b) Polystyrene content: 29% by mass,

(c) Mn=67,400,

(d) Polydispersity index: 1.40.

EXAMPLE 5 ##STR12##

The procedure of Example 3 was repeated, using 0.127 gram (6.1×10⁻⁴) ofBMEN and 0.90 ml (12.6×10⁻⁴ mole) of secondary BuLi. First, 24.5 grams(0.45 mole) were polymerized as described in Example 3. Thepolybutadiene sequence obtained under these conditions had an Mn valueof 41,000, a polydispersity index of 1.20, and a 1,4-structural contentof 92%. Polymerization was carried out as indicated in Example 3, byadding 10 grams styrene, or 0.096 mole, to the system.

After polymerization, a sequenced SBS copolymer having a molecularweight of Mn=59,000 was recovered. The polybutadiene content asdetermined by proton NMR (¹ H NMR) was 70% by mass.

While the invention has been described in terms of various preferredembodiments, the skilled artisan will appreciate that variousmodifications, substitutions, omissions, and changes may be made withoutdeparting from the spirit thereof. Accordingly, it is intended that thescope of the present invention be limited solely by the scope of thefollowing claims, including equivalents thereof.

What is claimed is:
 1. In a process for the anionic polymerization of atleast one ethylenically unsaturated monomer in the presence of an alkalimetal compound primer therefor, the improvement which comprises, as saidprimer therefor, a bifunctional primer naphthalene compound having thestructural formula (VI): ##STR13## wherein each R¹ is a linear, branchedor cyclic alkyl radical having from 1 to 12 carbon atoms, or asubstituted or unsubstituted aryl radical; each R² is a C₁ -C₆ alkylradical, a C₅ -C₁₂ cycloalkyl radical, or an aromatic radical; and eachM" is an alkali metal.
 2. The process as defined by claim 1, said atleast one ethylenically unsaturated monomer comprising a diene,vinylaromatic and/or (meth)acrylic monomer.
 3. The process as defined byclaim 2, carried out in a nonpolar solvent.
 4. The process as defined byclaim 2, comprising the preparation of a trisequenced block copolymer.5. The process as defined by claim 2, comprising the polymerization ofbutadiene, isoprene, styrene, methyl methacrylate, or mixture thereof.